code: def test_doc_differentiates(self):
      a = sentinel("sentinel-name", "original-doc")
      with self.assertRaises(ValueError) as e:
          sentinel(a.__name__, "new-doc")
  
      msg = str(e.exception)
      self.assertIn(a.__name__, msg)
      self.assertIn(a.__doc__, msg)
  
file_path: catalyst/tests/utils/test_sentinel.py
imports: from copy import copy, deepcopy
  from pickle import loads, dumps
  from unittest import TestCase
  from weakref import ref
  from catalyst.utils.sentinel import sentinel
label_desc: Use image node_id 4 for calling the SentinelTestCase obj's underlying member method code with example usage: obj.test_doc_differentiates() without return types